Questionnaire and biochemical measures of smoking were studied in 211 hospital outpatients. Eleven different tests of smoke intake were compared for their ability to categorize smokers and nonsmokers correctly. The concentration of cotinine, whether measured in plasma. saliva. or urine, was the best indicator of smoking. with sensitivity of 96-97 per cent and specificity of 99-100 per cent. Thiocyanate provided the poorest discrimination. Carbon monoxide measured as blood carboxyhaemoglobin or in expired air Introdluction Self-reports of smoking status may not always be reliable, particularly in situations where smokers feel under strong pressure to give up smoking but have not been able to achieve this.'-3 A number of biochemical markers have been used to validate claims of nonsmoking, including measures based on thiocyanate,4-7 nicotine,8 cotinine,9-" and carbon monoxide.4 6"" These measures differ widely in availability, cost, and ease of administration. Measures based on nicotine have the advantage of being specific to tobacco but require expensive laboratory instrumentation. Levels of thiocyanate and carbon monoxide are easier to determine but may be raised through exposures unrelated to smoking, such as traffic emissions and diet. Few studies have attempted to compare the various biochemical tests." We report here a study in which all the markers of smoking currently in widespread use are compared for their ability to categorize smokers and nonsmokers correctly. Methods SubjectsThe subjects for the study were 215 outpatients at St.Mary's Hospital, London. On arrival for their clinic appointment, they were asked to fill in a self-completion questionnaire giving details of smoking habits and to provide samples of blood, expired air, saliva, and urine. There was no prior warning of the survey, but consent for the biochemical tests was obtained before completion of the questionnaire. gave sensitivity and specificity of about 90 per cent. Sensitivities of the tests were little affected by the presence among the claimed nonsmokers of a group of 21 "deceivers" who concealed their smoking. It is concluded that cotinine is the measure of choice, but for most clinical applications carbon monoxide provides an acceptable degree of discrimination and is considerably cheaper and simpler to apply. (Am J Public Health 1987; 77:1435-1438 cigarette smokers at some time and 90 (43 per cent) said that they were current smokers of cigarettes, pipes, or cigars. Reported mean cigarette consumption in the cigarette smokers was 13.2 cigarettes per day, and 97 per cent reported having smoked on the test day. with a mean time since last cigarette of 1.5 hours.The concentration of nicotine and cotinine in plasma, saliva, and urine was determined by gas chromatography.'3"14 Carboxyhaemoglobin concentrations were measured with an IL282 CO-Oximeter and carbon monoxide in expired air after breath-holding with a portable CO analyzer incorporating an ethanol filter.'5 Thiocyanate was measured by an automated modification of the A...

The addition of transdermal nicotine to conventional maintenance therapy improves symptoms in patients with ulcerative colitis.

Objective To examine the associations between a biomarker of overall passive exposure to tobacco smoke (serum cotinine concentration) and risk of coronary heart disease and stroke. Design Prospective population based study in general practice (the British regional heart study). Participants 4729 men in 18 towns who provided baseline blood samples (for cotinine assay) and a detailed smoking history in 1978-80. Main outcome measure Major coronary heart disease and stroke events (fatal and non-fatal) during 20 years of follow up. Results 2105 men who said they did not smoke and who had cotinine concentrations < 14.1 ng/ml were divided into four equal sized groups on the basis of cotinine concentrations. Relative hazards (95% confidence intervals) for coronary heart disease in the second (0.8-1.4 ng/ml), third (1.5-2.7 ng/ml), and fourth (2.8-14.0 ng/ml) quarters of cotinine concentration compared with the first ( ≤ 0.7 ng/ml) were 1.45 (1.01 to 2.08), 1.49 (1.03 to 2.14), and 1.57 (1.08 to 2.28), respectively, after adjustment for established risk factors for coronary heart disease. Hazard ratios (for cotinine 0.8-14.0 v ≤ 0.7 ng/ml) were particularly increased during the first (3.73, 1.32 to 10.58) and second five year follow up periods (1.95, 1.09 to 3.48) compared with later periods. There was no consistent association between cotinine concentration and risk of stroke. Conclusion Studies based on reports of smoking in a partner alone seem to underestimate the risks of exposure to passive smoking. Further prospective studies relating biomarkers of passive smoking to risk of coronary heart disease are needed.

Summary and conclusionsBlood nicotine and carboxyhaemoglobin (COHb)

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